`collectCaptures` in `src/ir/lower.zig` was the closure free-variable
analyzer that decides which names from a closure body need to be
boxed into the env struct at lambda-build time. Its switch on AST
node kind enumerated every other shape (`.call`, `.if_expr`,
`.match_expr`, `.for_expr`, etc.) but no arm for `.ffi_intrinsic_call`,
so the trailing `else => {}` quietly dropped its `args[]` and
`return_type` walks. Names referenced inside `#objc_call(T)(recv,
"sel:", ...)` from a closure body never made it into the captures
list, so when lowering bound the closure scope from env, those names
came back as "unresolved".
The fix adds the missing arm — walk `return_type` and every `args[i]`
the same way `.call` walks `callee` + `args`.
Companion changes:
- `examples/issue-0038.sx` → `examples/103-ffi-closure-capture.sx`
(out of the open-issue namespace; comment header tightened to
describe the feature, not the historical bug).
- `examples/ffi-objc-call-09-in-construct.sx` drops the
`g_hasher_recv` module-global workaround that was added for this
bug — the closure now captures `recv` from `make_hasher`'s arg
list normally.
108/108 regression tests pass (+ffi-objc-call-09-in-construct,
+issue-0038 from the prior commit).
One trivial Obj-C call (`[obj hash]` returning NSUInteger) routed
through four sx surface constructs:
1. struct method body Probe.fetch
2. protocol impl method body impl Hashable for Probe
3. closure value body make_hasher
4. generic function body hash_through(recv: $T)
No new ABI shapes touched — pins that the `objc_msg_send` lowering
emits identical call shapes regardless of enclosing scope. Each
case validates the result `h_N == h_1` after threading `recv`
appropriately for each context.
The closure path reaches `recv` via a module-level global rather
than capturing the surrounding parameter — issue-0038 (prior
commit) documents the closure free-variable analyzer missing the
`FfiIntrinsicCall` node, with a clean workaround pinned.
